Spin-on type filters are used to filter lubricating oil and hydraulic oil for devices such as engines, air compressors, various types of hydraulic machines, and the like. Generally, spin-on filters have deep drawn, sheet metal canisters in which an annular filter element is disposed, which filter element is retained by an end plate that is in turn secured within the canister by an annular metal cover. In addition to holding the annular filter element in the canister, the end plate provides a flow path to and from the filter element, and includes a central threaded aperture so that it may be "spun on" or threaded to the machine or engine with which it is used.
For some applications, such as hydrostatic transmissions, a filter must be capable of withstanding continuous cyclic pressure surges of up to 500 psi or sustain periods without fatigue failure and leakage. This means that the burst pressure must be increased for such applications.
High performance filters also require large outlet ports through the end plate and as a result, only a relatively small end plate area remains outboard of the outlet port. That area is perforated to form inlet ports which can further compromise the strength of an end plate. This has resulted in the use of expensive die cast aluminum end plates, which require high tooling costs, and high costs for maintaining the tooling. In addition, there are relatively long manufacturing cycle rates and significant secondary machinery associated with manufacturing such end plates.
Accordingly, there is a need for end plates which increase the burst pressure of a standard welded plate/cover spin-on filter cartridges without a major increase in plate thicknesses and expense.